1. Field of the Invention
The present invention relates to a head assembly in which the flying height of a head slider varies according to the operational state, and a drive system adopting the same.
2. Description of the Related Art
A hard disk drive system has at least one magnetic head corresponding to a recording/reproducing surface of a hard disk that is rotating. The magnetic head writes or reads information by magnetizing or detecting a magnetic field of a surface of the hard disk drive.
In a hard disk drive system, read/write is performed in a swing arm driving manner in which a magnetic head assembly is installed on a base to pivot and a magnetic head installed at one end of the magnetic head assembly is moved to a desired position on a rotating disk as the magnetic head assembly pivots.
Referring to FIG. 1, a typical hard disk drive system 10 includes a hard disk 20 installed on a base 11 to rotate when a predetermined information is recorded, and a magnetic head transferring apparatus to transfer a magnetic head 50 to a desired track position on the hard disk 20 to write and read information of the hard disk 20. Here, the hard disk 20 is divided into a recording area 22 where information is recorded and a parking area 21 where the magnetic head 50 is parked when the hard disk 20 stops rotating.
The magnetic head transfer apparatus includes a magnetic head assembly 30 installed to pivot around a pivot shaft 30 provided on the base 11 and having the magnetic head 50 mounted thereon, and a driving portion 40 to pivot the magnetic head assembly 30 using an electromagnetic force.
The magnetic head assembly 30 includes a suspension 31 coupled to an end portion of an actuator arm 32 rotatably coupled to the pivot shaft 34, and a magnetic head slider 50 installed at the suspension 31 and having a magnetic head (not shown) for reading/writing information on/from the hard disk 20.
The magnetic head slider 50 is biased toward the hard disk 20 by the suspension 31. When the hard disk 20 begins to rotate, the magnetic head slider 50 flies by being lifted by an air dynamic pressure generated by the rotation of the hard disk 20. Here, the height at which the magnetic head slider 50 flies in a lifted state (hereinafter, referred to as the “flying height (FH)”) is determined by a gram load of the suspension 31 and lift by air flow according to the rotation of the hard disk 20. The flying height is a gap between a surface of the hard disk 20 and a read sensor, that is, a magnetoresistance head, provided at the tip end of the magnetic head slider 50 when the magnetic head slider 50 flies by being lifted with respect to the hard disk 20 during the rotation of the hard disk 20. The gram load refers to a force exerted by the suspension 31. A high gram load corresponds to a stiff suspension.
FIG. 2 shows a structure of a typical magnetic head 70. As shown in the drawing, the magnetic head 70 includes a magnetoresistance head 74 for reproduction, and an induction recording head for recording. The magnetoresistance head 74 detects and reads out a magnetic signal recorded in the hard disk 20. The induction recording head for recording a desired signal in the hard disk 20 includes a top pole 71 and a bottom pole 72 for forming a leakage magnet toward the hard disk 20, and a recording coil 73 for generating a magnetic field according to the supply of current.
Recently, to increase capacity of the hard disk 20, a track per inch (TPI) is increased while the width W of a track is decreased.
To reduce the width of a track of the hard disk 20, the width of a write head to write a magnetic signal on the track of the hard disk 20 should be reduced accordingly. Also, the flying height of the magnetic head 70 needs to be lowered to read out a magnetic field written on a track having a relatively small size.
When the flying height of the magnetic head 70 is lowered, the gap between the magnetic head slider 50 and the hard disk 20 decreases so that the magnetic head slider 50 may actually contact (be interfered by) the hard disk 20, moving the magnetic head slider 50 to another track or the parking area 21 of the hard disk 20. As a result, the magnetic head 70 or the hard disk 20 can be damaged.
Thus, it is necessary to reduce interference between the magnetic head slider 50 and the hard disk 20 by increasing the flying height of the magnetic head 70 according to the operational state, for example, when the magnetic head slider 50 is moved to another track or the parking area 21 of the hard disk 20.
FIG. 3 is a perspective view illustrating an example of a conventional magnetic head assembly disclosed by Japanese Patent Publication No. 7-85621 to reduce interference between the magnetic head slider and the hard disk.
Referring to the drawing, a conventional magnetic head slider 80 includes a magnetic head slider 81 having a magnetic head, a flexible member 83 for supporting the magnetic head slider 81, a support spring structure 85 coupled to the flexible member 83 and applying a load weight to the magnetic head slider 81, and a piezoelectric element 87 installed at the magnetic head slider 81 to change a weight point of the magnetic head slider 81. The piezoelectric element 87 is installed to be capable of extending inside the magnetic head slider 81.
Thus, as a voltage is applied to the piezoelectric element 87, the piezoelectric element 87 is extended. Accordingly, the weight point of the magnetic head slider 81 is changed. FIG. 4 shows a change in the flying height of the magnetic head slider 81 according to a change in the weight point of the magnetic head slider 81. In FIG. 4, L denotes the length of the magnetic head slider 81, I1 and I2 denote the distances from one side of the magnetic head slider 81 to the weight point in a lengthwise direction. Assuming that when the weight point is located at I1 the flying height of the magnetic head slider 81 with respect to the hard disk 20 is h1, and when the weight point is located at a position separated by the distance I2 from one side of the magnetic head slider 81 in the lengthwise direction wherein I2 is greater than the distance I1, the flying height h2 is lower than h1.
Thus, the conventional magnetic head assembly 80 can adjust the flying height of the magnetic head slider 81 by applying a voltage to the piezoelectric element 87.
However, in the above-described conventional magnetic head assembly 80, since a process of taking out part of the magnetic head slider 81 to install the piezoelectric element 87 is needed, the manufacturing process is complicated and uniform performance cannot be guaranteed during mass production of the magnetic head assembly 80.
Also, since the conventional magnetic head assembly 80 uses an indirect control method in which the flying height is adjusted by changing the inclination of the magnetic head slider 81 generated when the weight point of the magnetic head slider 81 changes, an accurate control of the flying height is difficult.
Also, since the conventional magnetic head assembly 80 needs a great change in the volume of the piezoelectric element 87 to change the weight point of the magnetic head slider 81, a control sensitivity in changing the flying height is lowered so that a fine control of the flying height is difficult. Furthermore, changing the flying height of the magnetic head slider 81 to switch an operation mode takes a long time so that a quick control is not possible.